OverscrollController consumes scroll updates only during gesture-nav.

content/test/data/overscroll_navigation.html

Index: content/test/data/overscroll_navigation.html
diff --git a/content/test/data/overscroll_navigation.html b/content/test/data/overscroll_navigation.html
index e4f2500db14b43633cc78235affddd7db70af0e0..fb1d7412a996cee9a756ace29a7fc5b05b131442 100644
--- a/content/test/data/overscroll_navigation.html
+++ b/content/test/data/overscroll_navigation.html
@@ -28,6 +28,8 @@
 
 <script>
 
+window.touchmoveCount = 0;
+
 function get_current() {
   if (location.hash.length == 0)
     return 0;
@@ -49,10 +51,22 @@ function navigate_prev() {
 function touch_start_handler() {
 }
 
+function touch_move_handler() {
+  window.touchmoveCount++;
+}
+
 function install_touch_handler() {
   document.addEventListener('touchstart', touch_start_handler);
 }
 
+function install_touchmove_handler() {
+  document.addEventListener('touchmove', touch_move_handler);
+}
+
+function reset_touchmove_count() {
+  window.touchmoveCount = 0;
+}
+
 function uninstall_touch_handler() {
   document.removeEventListener('touchstart', touch_start_handler);
 }